[Mesa-dev] [PATCH] i965/blit: Remove Yf/Ys tiled check under a FIXME at can_fast_copy_blit

[Anuj Phogat]

On Tue, Dec 6, 2016 at 4:26 PM, Anuj Phogat <anuj.phogat at gmail.com> wrote:
> On Tue, Dec 6, 2016 at 10:58 AM, Alejandro Piñeiro <apinheiro at igalia.com> wrote:
>> The FIXME suggest that the check should be removed.
>>
> Only if we see any performance or feature benefits in doing that.
> Last I checked I didn't see any performance benefits on Skylake.
and that was more than 6 months back. Things might be different now.

> I also couldn't figure out the cause of random failure in a piglit test:
>  ./bin/texelFetch fs sampler2DMSArray 4 98x1x9-98x129x9 -auto -fbo
>
> I'm still seeing this failure when I tested your patch with Jenkins CI system.
> Test passes when I run it locally on my system.
>
>> This change helps the following test:
>> GL45-CTS.texture_cube_map_array.color_depth_attachments
>>
>> to pass consistently on Skylake GT3e. Without this patch, on
>> Skylake GT3e that test has a ~76% pass rate, with some random
>> intel_do_flush_locked errors now and then.
>>
> By removing this check you're actually enabling fast copy blit on SKL+
> for all the tiling formats. So, now the driver will use XY_FAST_COPY_BLT
> in place of XY_SRC_COPY_BLT. If this change is fixing a test case for
> you, that's not because this is the right fix, but that's because you're
> avoiding to use XY_SRC_COPY_BLT.
> XY_SRC_COPY_BLT might be causing intel_do_flush_locked errors
> and the test failure. We need to dig in there to find the real cause.
>
>> It works fine on Skylake GT2, though.
>> ---
>>
>> I didn't analyze too much the code. It was more git history analysis.
>>
>> When I started to work to solve that test, I remembered that there was
>> a time in the past that worked, so I just did a git bisect. The more
>> recent bad commit I found was df210f. In any case, that one just fixed
>> that check, as became broken with commit 0c02d7. The one that added
>> the check (and the FIXME) was commit 412c8c.
>>
>> As the commit message says, that FIXME seems to suggest that is a
>> provisional change. Although I recognize that the failure is really
>> specific (for a Skylake model, not failing always), removing the check
>> gets the test pass consistently, and as far as I see, it didn't
>> introduce any regression.
>>
>>  src/mesa/drivers/dri/i965/intel_blit.c | 8 --------
>>  1 file changed, 8 deletions(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/intel_blit.c b/src/mesa/drivers/dri/i965/intel_blit.c
>> index 03a35ee..9f3b4d1 100644
>> --- a/src/mesa/drivers/dri/i965/intel_blit.c
>> +++ b/src/mesa/drivers/dri/i965/intel_blit.c
>> @@ -487,14 +487,6 @@ can_fast_copy_blit(struct brw_context *brw,
>>     if (brw->gen < 9)
>>        return false;
>>
>> -   /* Enable fast copy blit only if the surfaces are Yf/Ys tiled.
>> -    * FIXME: Based on performance data, remove this condition later to
>> -    * enable for all types of surfaces.
>> -    */
>> -   if (src_tr_mode == INTEL_MIPTREE_TRMODE_NONE &&
>> -       dst_tr_mode == INTEL_MIPTREE_TRMODE_NONE)
>> -      return false;
>> -
>>     if (logic_op != GL_COPY)
>>        return false;
>>
>> --
>> 2.9.3
>>